Abstract:

The acoustic emission (AE) signal characteristics were measured under different inlet gas velocity of gas solid fluidized bed. The hydrodynamics of the bed and the transition velocity from bubbling to turbulent fluidization were investigated by acoustic energy and recurrence quantification analysis (RQA). Because the acoustic energy analysis could not distinguish the regime transition velocity at different bed height, RQA was further applied to analysis the acoustic signals due to its ability to predict periodicity of a system. The results of RQA indicated that the motion of solids was more periodic when the bed was at the bubble regime compared to the turbulent regime. And the transition velocity of the solids at the lower bed height calculated by RQA was higher than that at the higher bed height. Therefore, the acoustic emission technique based on RQA should be an effective way to monitor the transition of flow regimes in the gas-solid fluidized bed and indicate the process of regime transition at different bed heights.

Key words: fluidized bed, transition, acoustic emission, measurement, recurrence analysis

摘要：

利用声发射技术采集不同流化气速下流化床内颗粒与壁面碰撞的声信号，结合声能量及递归分析法研究不同流型下颗粒运动特征，得到鼓泡流态化到湍动流态化的临界转变速度及流型转变规律。特别是针对声能量分析无法准确区分不同床层高度处流型转变的不足，利用递归分析可有效预测系统周期性的特点，将声信号进行递归分析，研究了流化床不同位置的流型转变性质。结果表明，鼓泡流态化下颗粒运动的周期性较湍动流态化强，并能够清晰地检测到由鼓泡流态化向湍动流态化的流型转变速度，而且床层较低处的流型转变速度比床层较高处大。由此获得了一种便捷灵敏、安全环保的非侵入式流化床流型转变速度的测量技术，可用于对整个流化床内不同位置流型转变过程的实时在线监控。

关键词: 流化床, 过渡, 声发射, 测量, 递归分析